The present invention is directed to the manufacture of a rotor core and is specifically directed to manufacture of a rotor core such that machining of an outer radial periphery of the rotor core is unnecessary.
A rotor core for an electric induction motor may be made by various techniques. One particular technique for manufacturing a rotor core is a conventional die-cast apparatus. Rotor core laminations are provided as a lamina stack within the conventional die casting machine. The die is closed, and molten material (e.g., metal) is injected into the die to form conductor end rings and bar windings, or the like, in engagement with the lamina stack. Such conventional die casting results in excess molded metal being present after the casting is complete. In particular, excess molded metal is present on the arcuate outer radial periphery of the rotor core. Such excess metal may be present on the arcuate outer periphery of the lamina stack.
Such excess metal must be removed via machining, grinding, or the like. In one example, the removal of excess metal is associated with a manual labor input. Further, the machining, grinding, or the like must be accomplished such that the outside periphery of the rotor core maintains a required acceptable dimensional tolerance. Still further, the machining, grinding, or the like must be performed such that the electrical properties of the rotor core are not degraded. Accordingly, it is to be appreciated that improvements to the state of the art are possible.
In accordance with one aspect, the present invention provides an apparatus for making a rotor core. The apparatus includes a support for supporting a lamina stack that has an axis extending along the stack. The apparatus includes a plurality of collets. A collet moving mechanism moves the collets radially inward against the lamina stack. An arrangement receives casting material that is cast to the lamina stack while the collets are against the lamina stack.
In accordance with another aspect, the present invention provides a method of making a rotor core. A lamina stack that has an axis extending along the stack is supported. A plurality of collets is placed about a radially outer periphery of the lamina stack. The collets are moved radially inward against the lamina stack. Material is cast to the lamina stack while the collets are against the lamina stack.